Add close-buttons to the select-open-window-pane

Add close-buttons to the select-open-window-pane which, if you click a ‘x’-button, the related open-window gets closed:

Preferably just closing the open-window for which you click on the ‘x’-button and keep this select-open-window pane open, so you can click several ‘x’-buttons and still have this select-open-window-pane open.